1. Field of the Invention
The present invention is generally related to a jet drive marine propulsion system and, more specifically, to a jet drive system that incorporates a positive displacement water pump in order to draw water from a body of water and pump the water to a cooling system of an internal combustion engine.
2. Description of the Prior Art
Many different types of jet drive marine propulsion systems are well known to those skilled in the art.
U.S. Pat. No. 3,994,254, which issued to Woodfill on Nov. 30, 1976, discloses a transmission for a marine jet drive. The device includes a multiple-high speed transmission for coupling an engine to the impeller of a marine jet drive, in such a way that an overdrive connection powers the jet drive under operating conditions up to a predetermined upper limit of cruising speeds and such that a reduced drive, for example a direct-drive connection, is automatically established for jet-drive speeds in excess of the cruising conditions.
U.S. Pat. No. 5,713,768, which issued to Jones on Feb. 3, 1998, discloses an intake housing for a personal watercraft. A personal watercraft (PWC) jet propulsion system has a hull design and an intake housing to optimize the structural integrity of the hull and facilitate efficient installation of the jet propulsion system without sacrificing proper alignment of the components of the jet propulsion system. The watercraft hull includes a recess defined by an inclined bulkhead spanning between two substantially vertical side walls. The inclined bulkhead contains an opening between the engine compartment within the hull and the components of the jet propulsion system.
U.S. Pat. No. 3,945,201, which issued to Entringer on Mar. 23, 1976, discloses a marine jet drive shift control apparatus. A marine jet drive unit includes a continuously running pump. A reversing gate is positioned partially or wholly within the forward jet to establish a corresponding reverse jet. For neutral drive, the gate is positioned such that the reverse jet just balances the forward jet. A remote shift control unit includes a detent means for locating and holding a rotatable shift lever in neutral. The detent means includes a pair of detent pins carried by a plate which is connected to a support wall by a slot and bolt lost motion connection.
U.S. Pat. No. 6,004,173, which issued to Schott on Dec. 21, 1999, discloses a marine propulsion system with a bypass eductor. A jet propulsion system is provided for a watercraft in which the secondary flow channel allows water to flow around the impeller region and bypass the impeller blades under certain conditions. The bypass feature provided by the secondary flow channel decreases static inlet pressure and improves the operation of the marine propulsion device at high speeds. In addition, the secondary flow channel increases the total mass flow of water through the steering rudder and therefore improves the steering when the propulsion system is being rapidly decelerated, such as during sudden stopping conditions.
U.S. Pat. No. 5,713,769, which issued to Jones on Feb. 3, 1998, discloses a stator and nozzle assembly for a jet propelled personal watercraft. A jet propulsion system for a personal watercraft provides a converging stator that can be manufactured using die-cast manufacturing techniques. The stator preferably has a stator housing having a substantially cylindrical inner surface, a stator hub, and seven equally spaced stator vanes supporting the hub coaxially in the stator housing. The cylindrical inside surface of the stator housing does not extend rearwardly as far as a conventional housing for a converging stator. The coaxial hub has a converging diameter portion that is located at least in part downstream or rearward of the stator housing.
U.S. Pat. No. 5,876,258, which issued to Gray on Mar. 2, 1999, discloses a self-activated marine jet drive weed grate cleanout system. The weed grate for a watercraft having a jet propulsion unit is described. It includes a plurality of cantilever tines each joined to a pivot rod. The cantilever tines extend across the inlet opening for the jet drive to prevent debris from entering through the water inlet opening. A spring member is mounted between the cantilever tines and a mounting frame such that the spring member provides an outward rotational bias force against the rotatable cantilever tines.
U.S. Pat. No. 4,026,235, which issued to Woodfill on May 31, 1977, discloses a jet drive apparatus with non-steering jet reverse deflector. A jet drive pump is secured to the boat transom and includes a gimbal ring pivoted on a horizontal trim access and a steering nozzle is pivotally mounted on a vertical pivot axis within the gimbal ring for steering. A trim linkage is connected to position the gimbal ring for trimming of the nozzle. A reversing gate is pivotally mounted on the same trim axis and connected by a mechanical coupling linkage with swivel and pivoting joints to the gimbal ring. The linkage has an axially sliding shift shaft in a rotatable shift lever for rotation about an axis perpendicular to the trim axis.
U.S. Pat. No. 3,906,885, which issued to Woodfill on Sep. 23, 1975, discloses a marine jet drive with power trim control and auxiliary rudder steering. A marine jet drive apparatus includes a power trim unit coupled to a jet deflector for remote trim positioning of the jet and for controlling steering deflection of the jet to either side. An auxiliary rudder also coupled to the jet deflector to vary the effectiveness of the auxiliary rudder with the trim positioning is provided. The main jet deflector is a tubular extension of the jet nozzle and is mounted for trim positioning. The main jet deflector is a tubular extension of the jet nozzle and is mounted for trim rotation about a transverse axis by a gimbal ring. A powered trim control link is connected to the ring for setting of the jet with respect to the horizontal.
U.S. Pat. No. 5,759,074, which issued to Jones on Jun. 2, 1998, discloses an impeller mounting system for a personal watercraft. An impeller mounting system uses an impeller shaft having a tapered portion and an impeller hub having a coaxial opening with a corresponding tapered seat. The impeller hub is tightened onto the impeller shaft so that the tapered portion of the impeller shaft presses against the tapered seat of the coaxial opening in the impeller hub with sufficient force to prevent the impeller hub from slipping with respect to the impeller shaft when the impeller shaft rotates to drive the impeller hub. Static frictional forces between the tapered surfaces bear the entire rotational load for the jet drive, therefore reducing chatter noise and wear which can be caused by load bearing splines or the like.
U.S. Pat. No. 5,720,638, which issued to Hale on Feb. 24, 1998, discloses an engine driveshaft coupler for a personal watercraft. A jet propelled watercraft has a coupling assembly to couple an engine crankshaft to a jet pump impeller shaft. The coupling assembly can accommodate substantial engine crankshaft vibrations, yet effectively isolate the jet pump impeller shaft from transverse movement. The coupling assembly includes an engine crankshaft coupling head, an intermediate coupler, an impeller shaft coupling head, and two elastomeric isolators positioned between each of the coupling heads and the intermediate coupler. The intermediate coupler is supported exclusively by the elastomeric isolators and is allowed to tilt transverse to the rotational axis of the intermediate coupler to accommodate engine crankshaft displacement.
U.S. Pat. No. 6,033,272, which issued to Whiteside on Mar. 7, 2000, describes a marine jet drive system with a debris cleanout feature. The system is intended for use for a boat or the like and comprises a power plant for rotating a driveshaft. A gear system is connected to the driveshaft and is configured to engage and rotate an impeller shaft. An impeller mounted to the impeller shaft is enclosed within a housing having a water inlet opening and a jet stream exit opening. The gear system includes a pinion gear connected to the driveshaft and engaging a pair of opposed ring gears, the ring gears being thus rotatable by the pinion gear in opposite directions. A clutch system is provided for selectively causing the impeller shaft to alternatively be engaged by one or the other of the ring gears and thereby selectively rotating the impeller in opposite directions. By this arrangement, rotation of the impeller in a first direction draws water through the housing in normal fashion to provide thrust at the exit opening, while rotation of the impeller in the opposite direction reverses the flow through the housing causing debris to be flushed out of the impeller or inlet opening. A simple control system allows the boat operator to perform the flushing process while occupying the control station of the boat.
U.S. Pat. No. 3,601,989, which issued to Austin on Aug. 31, 1971, describes a marine propulsion system. The system includes a multistage, ducted pump creating a jet of propelling water which is driven from conventional power plants one being a relatively low horsepower diesel engine, the other a high output gas turbine. The former is connected to a single, large diameter first pump stage. The latter is connected to both the single, large diameter stage and the second smaller diameter stage, whereby the second stage is operated at a higher rotational speed. Suitable clutch means, preferably over running clutches provide for smooth transition from the diesel to turbine power mode and vice versa.
U.S. Pat. No. 6,244,913, which issued to Matsumoto et al. on Jun. 12, 2001, describes a propulsion unit assembly for a personal watercraft. The assembly provides for the quick and easy alignment of the propulsion device of the assembly relative to the longitudinal axis of the watercraft when mounting the propulsion device on the hull of the watercraft. The mounting arrangement includes a mounting plate having stoppers which cooperate with bosses formed on the front wall of the tunnel of the watercraft to properly align the mounting plate before fixing the plate to the hull and mounting the propulsion device thereto. In addition, the disclosed propulsion unit assembly includes an integrally formed cooling water supply system which utilizes the existing high-capacity jet pump unit to provide pressurized cooling water for cooling of the engine and associated watercraft components.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Jet pumps for use with personal watercraft or jet boats are well known to those skilled in the art. These marine propulsion devices support an impeller for rotation within a water passage, or channel, which has an inlet and an outlet. Water is drawn into the channel through the inlet from a body of water in which the marine vessel is operated and the water is accelerated by the impeller and ejected through the outlet which, in normal applications, includes a nozzle. The water that is ejected through the nozzle at the outlet of the water channel provides thrust that propels a watercraft. An engine is mounted in torque transmitting relation with the impeller shaft. The engine can be mounted with its crankshaft aligned vertically or horizontally. When the engine is mounted with its crankshaft supported for rotation about a vertical axis, a 90 degree transmission is typically provided to connect the vertical crankshaft in torque transmitting relation with the horizontal impeller shaft.
Several inherent conditions exist in conjunction with jet pumps used for propulsion of marine vessels. First, the impeller is normally used to provide a stream of water that is conducted to the engine and connected in fluid communication with the cooling system of the engine. The use of the impeller driven water stream to cool the engine creates two problems. First, the flow of water is affected not only by the rotational speed of the impeller but, in addition, by other factors such as the speed of the watercraft which changes the ram pressure of the water being forced into the inlet of the water channel in which the impeller rotates. This creates a magnitude of water flow to the cooling system of the engine which is not consistently proportional to the engine speed. Another problem relates to the fact that the engine cooling system requires that the impeller constantly remain in a rotating state in order to continually provide cooling water to the engine. The requirement for the continual rotation of the impeller, typically at elevated idle speeds, causes the watercraft to move even when the operator of the watercraft desires to remain at a stationary position. This type of creep of the watercraft is a direct result of the continual expelling of water through the nozzle. It would be significantly beneficial if a jet drive for a marine propulsion system could be provided in which it was not necessary to operate the impeller at elevated idle speeds in order to maintain sufficient cooling water to the engine. In addition, it would be beneficial if the cooling system of an engine for a jet drive marine propulsion system could be provided with a magnitude of cooling water flow that is generally proportional to the engine speed.